1. Field of the Invention
The present invention concerns a system, a device and a method thereof for monitoring a plurality of electric users, in particular household appliances connected in a network and belonging to a same household environment.
2. Background Information
As it is known, home automation, i.e. exploiting electronic technology in the household environment, whose aim is to cut down managing costs of the various users and develop new comfort, is getting more and more in use. This is substantially due to the following, reasons:                an increasing spreading of consumer electronics devices, such as videorecorders, HI-FI systems, satellite receiver systems, safety and theft-safe systems, personal computers, mobile telephones, etc.        the recent significant developments related to the control systems for household appliances, which are based on the use of microcontrollers and new sensors, and are able to dialog with the external world,        a progressive affirmation of communication bu standards, i.e. ruling systems defining the procedures for information exchange between the various household users and the physical means such information are transmitted onto.        
With reference to the latter point, it is particularly important to know that the communication means establishing itself as a standard in the household environment is the so-called power line, i.e. the power supply network whereto information can be sent in the form of amplitude or frequency modulated small signals. The use of such a means, in fact, allows connection of household users to the network without the need of introducing new or special wiring systems.
As a result, new opportunities based right on the use of the power line are created, which relate to the rationalization themes of energy consumption in the home and improved management of information associated with the various household users, in this frame, several proposals are already known, which are based on the use of control and supervision systems or devices for the household users, all of them characterized in that:                they perform automatic activity, even if against an appropriate operation by the utilizer or customer for their starting configuration;        they are classed at a hierarchical higher level compared to the household users level, i.e. developing an active control, with a master role, over them.        
A fully alternative solution to such a set “centralized” control and supervision approach of household users is disclosed in the European Patent Application EP-A-0 727 668, filed by the same Applicant hereto.
Such a document described a set of household appliances capable of constantly receiving information concerning the total power absorption of all household users (household appliances, illumination system, air conditioning system, etc.), concerning the maximum usable power (power supply contract), the current time (clock function) and the likely different electricity cost according to variable use hours rates.
Such information are applied by a special external sensor, which may be the same electric meter developed to that purpose, or an alternative device specifically provided. The means whereto such information are flowing may be of different type; however, the power line is a preferable one, i.e. the electric network itself, sine there is no noted for additional wiring.
The set of household appliances described in EP-A-0 727 668, each one equipped with a suitable electronic control system and adequate interfacing means to the network, is able to limit its own electric power consumption “spontaneously” and automatically, so as to maintain the total consumption of the whole household environment constantly below the limit established in the power supply agreement, requiring neither an external centralized supervision system nor any operation by the utilizer.